I want some ideas to increase the sales in my fitness center

Try to offer a class or a training session thru a daily site like Groupon or something similar. This way you get to advertise to a large number of potential members/clients and still make money out of the deal. I did this when I started my own business and I got a lot of new clients, which it would had been very hard for me to do in the amount of time it took to do it by using Groupon.

I hope this helps,

Harris